The present invention generally relates to an electronic structure that has in-situ formed unit resistors and a method for fabrication such structure and more particularly, relates to a semiconductor structure that has in-situ formed unit resistors fabricated of a refractory metal alloy having a resistivity of at least 100 xcexa9-cm and a method for fabricating the structure.
In conventional electronic devices, resistors are electrically connected to a circuit board to provide specific electrical resistances to an electronic circuit.
In semiconductor devices, it has been difficult to provide resistors inside a semiconductor structure. Particularly, it has not been possible to form by an in-situ method resistors in a semiconductor structure that provide high resistance in the range of more than several thousand xcexa9/square. The only resistor designed for use in a semiconductor device has been a diffusion resistor which is built on the surface of a semiconductor substrate. The resistivity of a diffusion resistor is in the range between about 100 xcexa9/square and about 4,000 xcexa9/square. To date, it has not been possible to build unit resistors inside a semiconductor structure, and particularly, to built unit resistors in a vertical direction of the structure. One reason for such difficulty is the unavailability of a material that can be used in a semiconductor fabrication process that has sufficiently high electrical resistivity.
It is therefore an object of the present invention to provide an electronic structure that has in-situ formed unit resistors therein that does not have the drawbacks or shortcomings of the conventional diffusion resistors.
It is another object of the present invention to provide an electronic structure that has in-situ formed unit resistors therein by using a high resistivity refractory metal alloy.
It is a further object of the present invention to provide an electronic structure that has in-situ formed unit resistors therein that are situated in a vertical direction of the structure.
It is still another object of the present invention to provide an electronic structure that has in-situ formed unit resistors therein that are formed of electrically resistive vias.
It is another further object of the present invention to provide an electronic structure that has in-situ formed electrically resistive vias therein wherein the vias are formed of a material having a resistivity of at least 100 xcexa9-cm.
It is yet another object of the present invention to provide an electronic structure that has in-situ formed unit resistors which are formed of a refractory metal-silicon-nitrogen material.
It is still another further object of the present invention to provide a method for forming a semiconductor structure that has in-situ formed unit resistors therein by first forming a plurality of conductive elements, then a plurality of electrically resistive vias in electrical communication with the plurality of conductive elements, and then a plurality of conductive elements in electrical communication and on top of the plurality of electrically resistive vias.
It is yet another further object of the present invention to provide an electronic structure that has an in-situ formed unit resistor in electrical communication with a capacitor which includes a unit resistor formed of a high resistivity refractory metal alloy juxtaposed to and in electrical communication with the capacitor.
In accordance with the present invention, an electronic structure that has in-situ formed unit resistors and a method for fabricating such structure are provided. The invention further provides an electronic structure that has in-situ formed unit resistors juxtaposed to and in electrical communication with a capacitor.
In a preferred embodiment, an electronic structure that has in-situ formed unit resistors is provided which includes a pre-processed substrate which has a first insulating material layer on top; a first plurality of conductive elements formed on the first insulating material layer; a second insulating material layer overlying the first plurality of conductive elements and the first insulating material layer; a plurality of electrically resistive vias that has a resistivity of at least 100 xcexa9-cm formed, in the second insulating material layer wherein each of the first plurality of conductive elements in electrical communication with at least one of the plurality of electrically resistive vias; and a second plurality of conductive elements formed on top of the second insulating material layer each in electrical communication with at least one of the plurality of electrically resistive vias.
In the electronic structure that has in-situ formed unit resistors, the pre-processed substrate may be a semiconductor wafer that has a first dielectric material layer formed on top, the pre-processed substrate may be formed of an electrically insulating material selected from the group consisting of glass, ceramic and polymeric materials. The plurality of electrically resistive vias may be formed of a refractory metal-silicon-nitrogen material, or may be formed of a refractory metal-silicon-nitrogen material wherein the refractory metal is selected from Ta, Nb, V, W or Ti. The plurality of electrically resistive vias may be formed of TaSiN which has a composition of between about 10 at. % and about 55 at. % Ta, between about 10 at. % and about 45 at. % Si, and between about 30 at. % and about 80 at. % N. The plurality of electrically resistive vias each has a diameter between about 0.1 xcexcm and about 100 xcexcm, and a height between about 10 nm and about 1,000 nm. The plurality of electrically resistive vias may have a resistivity preferably of at least 150 xcexa9-cm.
The plurality of electrically resistive vias may be formed by depositing a TaSiN film layer into a plurality of via openings, wherein the TaSiN film layer may have a sheet resistance between about 0.3 M-xcexa9/square and about 1 K-xcexa9/square. The plurality of electrically resistive vias may further have a diameter preferably of about 1 xcexcm and a height preferably of about 100 nm. The first plurality of conductive elements and the second plurality of conductive elements may be formed of a material selected from the group consisting of doped polysilicon, metal silicide, polycide, refractory metals, aluminum, copper and alloys thereof. Each of the first plurality of conductive elements may be in electrical communication with two of the plurality of electrically resistive vias that are immediately adjacent to each other. Each of the second plurality of conductive elements may be in electrical communication with two of the plurality of electrically resistive vias that are immediately adjacent to each other.
The electronic structure that has in-situ formed unit resistors of the present invention may further include a third insulating material overlying the second plurality of conductive elements and the second insulating material layer; a second plurality of electrically resistive vias that has a resistivity of at least 100 xcexa9-cm formed in the third insulating material layer wherein each of the second plurality of conductive elements in electrical communication with at least one of the second plurality of electrically resistive vias; and a third plurality of conductive elements formed on top of the third insulating material layer each in electrical communication with at least one of the second plurality of electrically resistive vias, whereas at least one of the second plurality of electrically resistive vias is in electrical communication with at least one of said first plurality of electrically resistive vias.
The present invention is further directed to a method for forming a semiconductor structure with in-situ unit resistors by the operating steps of first providing a pre-processed substrate that has a planar top surface; depositing a first insulating material layer on the planar top surface of the pre-processed substrate; forming a first plurality of conductive elements on the first insulating material layer; depositing a second insulating material layer on top of the first plurality of conductive elements and the first insulating material layer; forming a plurality of via openings in the second insulating material layer, each of the via openings exposing one of the first plurality of conductive elements; depositing an electrically resistive metal that has a resistivity of at least 100 xcexa9-cm into the plurality of via openings forming a plurality of electrically resistive vias; and forming a second plurality of conductive elements on top of the second insulating material layer wherein each of the second plurality of conductive elements in electrical communication with at least one of the plurality of electrically resistive vias.
The method for forming a semiconductor substrate with in-situ unit resistors may further include the step of depositing the electrically resistive metal in TaSiN, or the step of depositing the electrically resistive metal by sputtering a Taxe2x80x94Si alloy target in the presence of nitrogen, or the step of depositing the electrically resistive metal by co-sputtering from Ta and Si targets in the presence of nitrogen. The method may further include the step of depositing the electrically resistive metal by co-depositing from a Ta target at a sputtering power of at least 50 W dc and a Si target at a sputtering power of at least 300 W rf. The method may further include the step of depositing the electrically resistive metal by evaporation or chemical vapor deposition. The method may further include the step of patterning a layer of the electrically resistive metal by reactive ion etching utilizing a photoresist mask, or the step of conducting the RIE by using a gas of Cl2/O2 or Cl2. The method may further include the step of forming the plurality of via openings each having a height between about 10 nm and about 1,000 nm, a diameter between about 0.1 xcexcm and about 100 xcexcm. The method may further include the step of removing excess electrically resistive material from a top surface of the second insulating material layer by chemical mechanical polishing.
The present invention is still further directed to an electronic structure that has an in-situ formed unit resistor in electrical communication with a capacitor which includes a unit resistor that is formed by a first conductive element and a second conductive element situated in different levels in the electronic structure connected therein between by an electrically resistive via, the electrically resistive via may be formed of a material that has a resistivity of at least 100 xcexa9-cm; and a capacitor formed juxtaposed to and in electrical communication with the unit resistor.
In the electronic structure that has an in-situ formed unit resistor in electrical communication with a capacitor, the capacitor may be a deep-trench capacitor or a stacked capacitor. The unit resistor may be electrically connected in-series with the capacitor, or electrically connected in-parallel with the capacitor. The unit resistor may be electrically connected to and situated on top of the capacitor, or electrically connected to and situated below the capacitor. The electrically resistive via may be formed of a refractory metal-silicon-nitrogen material wherein the refractory metal may be selected from the group consisting of Ta, Nb, V, W and Ti. The electrically resistive via may be formed of a diameter between about 0.1 xcexcm and about 100 xcexcm, and at a height between about 10 nm and about 1,000 nm.